The reason behind my questions is I make calls and I make variations to suit different people. I'd like to concentrate on the most popular features.

Personally, I prefer slate over glass, slightly proud of the edge of the pot so when I condition the slate I don't gouge up the pot. I'm carefull with my equipment so I don't worry about chipping the edges of the striking surface, but for looks I like it level or slightly below. Another advantage to having the surface slightly higher than the edge of the pot is you can lay the pot face down on sandpaper and condition the entire surface keeping it level.

Most calls are 3.5", but I make a few 3" and really like them since they are easier to hold.

For the slate over glass calls I like walnut or purple heart strikers so I can produce two different sounds on one call.

That said, if the weather is wet nothing beats a glass, crystal, ceramic, copper or aluminum surface with an acrylic or carbon striker.